Contact heating apparatus and method



Aug. I5, 1967 E. A. SALO 5 3,336,013

CONTACT HEATING APPARATUS ANDMETHOD I Filed June 24,, 1965 5 Sheets-Sheet l FIE-.3-

INVENTOR. ERIC 4. SALO Arm/ave Y5 Aug. 15, 3967 E. A. SALO 3,336,013

CONTACT HEATING APPARATUS AND METHOD Filed June 24, 1965 A s Sheets-Sheet 2 ATTOKNEYS Aug. 15, 1967 SALO 3,336,013

CONTACTHEATING APPARATUS AND METHOD Filed June 24, 1965 5 Sheets-Sheet s TURBINE GENE/3A TO)? I I 72.5Kw

BOILER C ONDE N 514 TE ONE N T T5 PUMP @2055 #64 T 9m 1 Ji fifm FEED PUMP PIE. 5.-

TURBINE GENE/M TOR BOILER I 7/.0 Kw

04 204 5 W 23 lco/vams/irs HEATER M 198 r PUMP v PUMP INVENTOR ERIC 4. SALO TWO 610550 HEATERS 6/?055 HEAT RATE /5,/00

FIE-.5-

ATTORNEYS United States Patent 3,336,013 CONTACT HEATING APPARATUS AND METHOD Eric A. Salo, an Lorenzo, Calif assignor to Eryx Corporation, San Lorenzo, Calif a corporation of California Filed June 24, 1965, Ser. No. 466,794

1 Claim. 81. 261-39) The present invention relates to an apparatus and method for heating a variable flow of fluid by direct contact with a heating fluid which may be at a lower pressure than the fluid being heated. More particularly, the invention is directed to such an apparatus and method facilitated for use in a steam cycle to heat a stream of high pressure condensate with a stream of'extraction steam at a lower pressure.

In the prior art, regenerative steam cycles wherein extraction steam is utilized to heat condensate feedwater are well known. The purpose of such regenerative steam cycles is to increase the efliciency of the Rankine cycle by removing a fraction of the steam, after partial expansion in the turbine, for use in increasing the temperature of the condensate returning to the steam generator. Typically, the condensate feedwater heaters employed in such regenerative cycles are of the shell and tube type. In the use of this type of heater, the extraction steam from the turbine is introduced into the shell and the condensate feedwater is pumped through the tubes within the shell. Thus, steam of virtually any pressure may be utilized to heat the condensate feedwater, even though the feedwater may be at a higher pressure. The latter characteristic particularly suits shell and tube heaters for use in regenerative cycles, since the condensate feed water being heated is typically at a higher pressure than the extraction steam.

Shell and tube type heaters have many disadvantages, however, inherent from their construction. Foremost among these disadvantages is the high expense of installation and maintenance. This expense results primarily from their large size and the extensive heating surfaces which are employed. It is well appreciated that these heating surfaces and the joints therein present an extremely high maintenance factor both with respect to the direct cost of maintenance and the nonproductive downtime of the steam cycle during such maintenance. Another disadvantage of shell and tube type heaters is that the gradual dissolving of their extensive heating surfaces functions to contaminate the condensate feedwater. Although this contamination progresses at a very slow rate, it presents a real problem when viewed over the life of a steam cycle system. Still another disadvantage of shell and tube type heaters is that they introduce a considerable pressure drop into the steam cycle. This drop must be made up by the addition of pumping power to the cycle. Naturally, this addition is expensive from a monetary standpoint both with respect to the installation of increased pumping facilities and the continued operation of these facilities.

Shell and tube type heaters also are disadvantageous from the thermodynamic standpoint in that the final temperature of condensate feedwater heated thereby cannot appreciably exceed the saturation temperature corresponding to the pressure of the heating steam at the point of entry into the heater. Thus, the degree to which the condensate feedwater may be heated in such heaters is directly dependent on the pressure of the heating steam at the point of entry. The latter pressure is, of necessity, limited to relatively low pressure in typical steam cycles.

It is, accordingly, a principal object of the present invention to provide a contact heating apparatus, system, and method which overcomes the aforediscussed disadvantages of shell and tube type heaters.

Another and more specific object of the invention is to provide a contact heating apparatus and method facilitating the introduction of relatively low pressure steam into a fluid stream at a higher pressure. With respect to this object, it is another and related object to provide such an apparatus and method wherein the heat absorbed by the fluid stream being heated is not limited by the pressure of the steam being utilized for heating.

Still another object of the invention is to provide a contact heating apparatus facilitated to control the introduction of stream into a fluid stream being heated. With respect to this object, it is a related object to provide such an apparatus adapted to control this introduction responsive to the condition of the heated fluid downstream from the point of steam introduction.

Yet another object of the invention is to provide a method to facilitate the controlled introduction of steam at a relatively low pressure into a fluid stream at a higher pressure responsive to the thermal condition of said stream downstream from the point of steam introduction.

The apparatus of the invention basically comprises a variable venturi constriction adapted to be introduced into a confined fluid stream to create a localized area of high velocity and low pressure. This constriction is provided at its throat portion with an opening to facilitate the introduction of steam into the localized area. In its more sophisticated forms, the constriction is provided with control means to selectively vary the cross sectional area of its throat portion. When incorporated into the invenive system, the control means of the apparatus is coupled to an actuating mechanism responsive to the thermal condition of the stream being heated downstream of the constriction.

In the inventive method, relatively low pressure steam is introduced into a confined fluid stream at a higher pressure by increasing the velocity of the stream at a localized area to lower its static pressure and then introducing the steam into the stream at this localized area to a degree where at least some of the steam is occluded in the stream. The velocity of the stream is then decreased downstream from said area to a degree where the static pressure thereof is raised sutficiently that the occluded steam is substantially absorbed in the stream. In the more specific forms of the method, the amount of steam introduced into the stream is controlled responsive to its thermal condition downstream of the localized area.

The foregoing and other objects and the specific details of the invention will become more apparent when viewed in light of the following description and accompanying drawings, wherein:

FIG. 1 is an elevational view, in vertical section, illustrating the venturi constriction of the inventive apparatus;

FIG. 2 is a plan view, partially in section, illustrating the venturi constriction of FIG. 1;

FIG. 3 is a sectional view taken on plane 3-3 of FIG. 1;

FIG. 4 is an elevational view of the inventive system, partially in section, showing the constriction of FIGS. 1, 2, and 3 and the thermally responsive actuating means therefor;

FIG. 5 is a heat balance diagram schematically illustrating a regenerative steam cycle incorporating the present invention; and

FIG. 6 is a heat balance diagram schematically illustrating a regenerative steam cycle incorporating a pair of conventional shell and tube type heaters Referring now to FIGS. 1, 2 and 3 of the drawings, the numeral 10 therein designates the contact heater of the apparatus in its entirety. The exterior of the heater is defined by a housing 11 having a condensate inlet 12 with a mounting flange 13 therearound and a condensate outlet 14 with a mounting flange 15 therearound. The housing 11 further includes a steam inlet 16 having a mounting flange 17 therearound. The steam inlet 16 communicates with a chamber 20 extending around the housing, which chamber is comprised of segments 21, 22, 23, and 24 connected in fluid communication through passages 25, 26, 27, and 28.

The interior of the housing 11 is defined by opposed sidewalls 31 and 32 fixed in spaced substantially parallel relationship; a downwardly bowed upper wall 33 fixed between the sidewalls 31 and 32; and an upwardly bowed lower wall mounted within the housing for movement towards and away from the upper wall 33. The lower wall is defined by a pair of longitudinally aligned segments 34 and 35 having opposed end portions pivotally secured to the housing 11 by hinge pins 36 and adjacent end portions secured together for movement towards and away from each other by a link 37. The hinge pins 36 are disposed so that the axes thereof traverse the housing 11 in substantially parallel relationship to each other. The link 37 is pivotally secured to the segment 34 by a hinge pin 40 extending through aligned openings in the link and segment. The link 37 is pivotally and slidably secured to the segment 35 through a hinge pin 41 extending through the segment into slidable engagement with a slot 42 in the link.

Movement of the lower wall defined by the segments 34 and 35 is facilitated by an actuating rod 43 extending slidably through the housing 11 and having one end pivotally secured to the link 37 by a hinge pin 44. The rod 43 is sealingly received in the housing 11 for slidable movement through means of a collar 45 integral with the housing; an annular packing gland 46 disposed between the collar and the rod; and a gland follower nut 47 threadedly disposed on the collar 45 to impart compression to the gland 46. As will become apparent from the subsequent discussion, suitable actuating means is secured to the end of the rod 43 remote from the housing 11.

In the construction illustrated in FIGS. 1, 2, and 3 the condensate inlet and outlet are shown coupled to a condensate conduit 50 through means of the flanges 13 and 15, respectively, and the steam inlet 16 is shown coupled to a steam conduit 51 through means of the flange 17. In this arrangement, condensate is forced through the venturi constriction defined by the inner walls of the housing and, as a result, a high velocity low static pressure area is cre ated at the throat of the constriction. In operation, this static pressure is maintained at a pressure less than that of the steam entering the housing through the conduit 51 by controlling movement of the segments 34 and 35. The preferred construction to effect this controlled movement will be developed subsequently.

Through the creation of the aforedescribed pressure characteristics within the venturi constriction, it is possible to inject the relatively low pressure steam entering the housing through the conduit 51 into a stream of condensate entering the housing at a pressure higher than the pressure of the heating steam at the point of entry. This injection is accomplished through openings 52 and 53 extending between the chamber 20 and the interior of the constriction throat. The opening 52 is defined by a transverse slot extending through the wall 30, while the opening 53 is defined by the space between the segments 34 and 35. The injection of steam into the condensate is further facilitated by a fluted portion 55,. fluted concurrent with the flow of condensate, formed on the segment 34 adjacent the opening 53 and an opposed substantially mating fluted portion 56 formed on the wall 33. These fluted portions function to extrude channels in the condensate passing over the openings 52 and 53, which channels have the effect of entraining steam in the condensate stream without turbulence.

The entrainment without turbulence of steam into the condensate at the low pressure throat area of the constriction is of particular heating benefit. Specifically, al-

though the heat of this entrained steam is not absorbed into the condensate at the low pressure of the throat area, it is absorbed downstream of the throat area upon divergence of the condensate stream and resultant increasing of its static pressure. This increase in static pressure naturally raises the saturation temperature of the steam and, thus, its heat absorption capability. From this it can be seen that the heat absorption of the condensate is not limited by the saturation temperature of steam injection pressure, as would normally be the case.

Referring now to FIG. 4, therein is illustrated a system for controlling the aforedescribed contact heater so that the condensate discharged therefrom is maintained at substantially saturation temperature. This system includes a thermal sensing device 57 and an actuating device comprised of a motion imparting mechanism 60 for the rod 43, which mechanism is coupled to the device 57 through a control mechanism'61.

The thermal sensing device 57 comprises a sealed chamber 62 sealingiy disposed within the conduit 50 through a flange connection 63; a fluidtight case 64 sealingly divided into compartments 65 and 66 by a diaphragm 67; a conduit 76 connecting the interior of the chamber 62 in fluid communication with the compartment 65; and, a conduit 71 connecting the interior of the condensate conduit 56 in fluid communication with the compartment 66. The chamber 62, conduit and compartment 65 communicating therewith are filled with water 72 to a degree where the water level 73 in the chamber is approximately at the centerline of the conduit 50. This water is preferably introduced into the chamber 62 in boiling condition through a threaded opening 74 in the upper end of the chamber. After being so filled, and while the water is still in boiling condition, the opening 74 is sealed with a plug 75. This procedure assures that the chamber 62 is evacuated of air and that only water vapor 78 occupies the volume of the chamber above the level 73.

In the preferred construction of FIG. 4, the chamber 62 is located downstream of the heater 65 at a point where the static pressure of the condensate stream is reestablished through divergence of its cross sectionad area and a resultant decrease in its velocity. Through this arrangement, the thermal condition sensed by the device 57 is that of the condensate stream after occluded steam injected thereinto at the heater 19 has been substantially absorbed. At this thermal condition, it is noted that the temperature of the condensate is considerably higher than that at the throat of the heater constriction. This results because, as a practical matter, maximum condensate temperature is limited to the saturation temperature of the condensate and, naturally, this saturation temperature increases as the condensate pressure increases.

In the operative condition illustrated in FIG. 4, one side of the diaphragm 67 is subjected to the vapor pressure within the chamber 62, while the other side of the diaphragm is subjected to the static pressure within the condensate conduit 50. In addition to these pressures, the diaphragm 67 is also subjected to equal and opposite static pressure heads by the columns of fluid within the conduits 7t) and '71. Thus, the position of the diaphragm 67 is directly dependent upon the differential in pressure between the interior of the chamber 62 and the interior of the conduit 50. As a result, the diaphragm 67 assumes the neutral position illustrated when the vapor pressure in the chamber 62 equals the static pressure in the conduit 50. In the latter condition, the condensate water in the conduit 50 must be at saturation temperature.

The latter conclusion follows from the fact that the water 72 and water vapor 78 are at the same temperature as the condensate water flowing around the chamber 62. At this temperature the pressure Within the chamber corresponds closely to the saturation pressure of the condensate flowing around the chamber. A transitory reduction of the temperature of the condensate water below the saturation temperature in the chamber 62 immediately results in a lowering of the vapor pressure of the water therein to the saturation pressure corresponding to the transitorily reduced water temperature, since the temperature within the chamber 62 and the water flowing therearound are normally the same. The lowered resulting temperature within the chamber 62 is hydraulically transmitted to the compartment 65, thus causing a force unbalance on diaphragm 6-7, and resultant movement of the diaphragm away from the relatively unalfected compartment 66. In the event of a transistory rise of condensate water temperature around the chamber 62, the corresponding increase in the saturation pressure within the chamber is transmitted to the compartment 65, thus unbalancing the pressure in the compartment 65 in relation to the compartment 66 and causing a movement of diaphragm 67 toward the left. From the subsequent discussion, it will be seen that movement of the diaphragm 67 functions through the motion imparting mechanism 60 to operate the control mechanism 61.

The motion imparting mechanism 60 simply comprises a double acting hydraulic cylinder 76 having a piston 77 movably disposed therein. This piston is connected to the actuating rod 43 of the contact heater 10. Thus, rectilinear motion of the piston 77 functions to vary the throat area of the venturi constriction in the heater. Movement is imparted to the piston 77 by introducing a differential pressure thereacross through means of pressure openings 80 and 81 extending through the cylinder 76.

The control mechanism 61 comprises a rod 82 secured to the diaphragm 67 and slidably and sealingly extending through the case 64; a post 83 supporting the rod 82 for rectilinear movement; adjustable biasing means including a nut 84 threadedly received on the rod and a coil spring 85 interposed between the nut and the post 83; a fourway valve 86 having a rotatable control block therein connected to the rod 82 through an arm 88; a pressure supply tube 91 connected between the interior of the conduit 50 and one side of the valve 86; a pressure exhaust tube 92 extending between the other side of the valve and a waste area; and cylinder control tubes 93 and 94 extending between the valve 86 and the openings 80 and 81, respectively. The connection between the rod 82 and the arm 88 comprises a slot 95 formed in the arm and a pin 96 secured to the rod 82 and slidably and pivotally received in said slot. Through this arrangement, rectilinear movement of the rod 82 is converted into rotational movement of the valve control block 87.

From the foregoing description, the operation of the control mechanism 61 is believed apparent. Specifically, when the valve control block 87 is turned responsive to movement of the rod 82, passages 97 and 98 within the block function to selectively connect the supply and eX- haust tubes 91 and 92 to the control tubes 93 and 94. Naturally, when the control block is in the neutral position illustrated, all of the tubes 91-94 are closed, thus maintaining the motion imparting mechanism 60 in a neutral condition.

In operation of the system illustrated in FIG. 4, increases in the pressure within the compartment 65 relative to the compartment 66 function to increase the throat area of the venturi constriction in the heater In a like manner, decreases in the pressure of the compartment 65 relative to the compartment 66 function to decrease the throat area of the venturi constriction in the heater 10. Thus, the amount of steam injected into the condensate through the heater 10 is controlled responsive to the condition of the condensate stream downstream from the heater. The amount of steam injected into the condensate of the heater 10 is controlled to maintain the downstream condensate at saturation temperature. When this temperature is reached, the system assumes the neutral position illustrated in FIG. 4.

In effecting control to increase condensate temperature, movement of the diaphragm 67 towards the compartment 65 is transmitted to the valve 86 as counterclockwise rotation which admits hydraulic pressure from the tube 91 into the lower volume of cylinder 76 which, in turn, causes upward movement of the piston 77. The latter movement causes the rod 43 to position the segments 34 and 35 closer to the wall 33, thus reducing the throat area of the venturi constriction and increasing flow velocity therethrough, with the result that the static pressure of the condensate at the throat of the constriction is reduced. By virtue of this pressure reduction, an increase in the heating steam flow is induced, thus restoring the temperature of water leaving the heater to saturation.

Control to decrease condensate temperature is similarly effected by movement of the diaphragm 67 towards the compartment 66. Specifically, this movement is transmitted as clockwise rotation to the valve 86 which, in turn, admits hydraulic pressure from the tube 91 into the upper volume of the cylinder 76 and causes downward movement of the piston 77. The latter movement lowers the rod 43 and connected segments 34 and 35 to a position increasing the throat area of the venturi constriction. This increased area functions to reduce the velocity of water at the throat, thus raising the static pressure and reducing the flow of heating steam into the heater. As a result, the temperature of water leaving the heater is lowered. This state continues until temperature stability is reached at saturation temperature at the chamber 62, as effected by pressure equalization in the compartments 65 and 66.

If it is desired to maintain the downstream condensate at slightly above saturation temperature, the spring may be compressed so as to induce a simulated condition of increased pressure in the compartment 66. When this condition is induced, the temperature of the downstream condensate will be increased to a point where the saturation pressure within the chamber 62 returns the control system to the neutral position illustrated. Similarly, if it is desired to maintain the downstream condensate at slightly below saturation temperature to avoid transitory raises of the temperature above saturation, the compression of spring 85 may be reduced to induce a simulated reduction of pressure in the compartment 66.

Referring now to FIGS. 5 and 6, therein are illustrated heat balance diagrams illustrating regenerative steam cycles incorporating the contact heating system of the present invention and typical prior art shell and tube type heaters, respectively. For the sake of comparison, the throttle steam output of the boilers in both cycles have been made identical, and the internal mechanical efliciency of the turbine is assumed identical for the two sets of calculations. Furthermore, in the prior art cycle of FIG. 6, two regenerative shell and tube type heaters have been incorporated in order to increase the eificiency of the cycle. In the cycles illustrated in both of these figures, the heat balance values at the various points have been derived through conventional steam table calculations.

The following legends apply to both FIGS. 5 and 6:

Main legends Q: flow-pounds per hour P: pressure-pounds per square inch absolute T: temperaturedegrees F.

It: heat-Btu per pound m: moisture-pounds per pound steam Subscript legends t: throttle c: condensate lp: low pressure ip: intermediate pressure d: drain fw: feedwater The increased efliciency of the FIG. 5 cycle as compared to that of the FIG. 6 cycle is best illustrated by a comparison of the generator outputs and the gross heat Z rates. For the sake of illustration, these are set forth below as follows:

FIG. (i.e., steam cycle incorporating inventive system) Gross heat rate, B.t.u. per kw. hr. 15100 Gross heat rate was calculated by the following formula:

From the foregoing description and particularly the comparison of the FIG. 5 and FIG. 6 heat balance cycles, it is believed apparent that the present invention provides both for increased efiiciency and simplicity in regenerative heat cycles. It is to be understood, however, that the invention is not intended to be limited to use in the particular heat cycles illustrated and described, but rather may be applied to any environment wherein it is desired to heat relatively high pressure fluid with steam at a lower pressure. Furthermore, it is to be understood that the foregoing detailed description of the invention is intended to be exemplary, rather than limiting. Accordingly, the invention is to be defined by the following claim.

What is claimed is:

Apparatus comprising:

(a) a housing having an inlet at one end and an outlet at the other end;

(b) venturi constriction means disposed Within said housing having a minimum area necked-down throat portion between said inlet and said outlet, said venturi constriction means comprising a pair of opposed Walls and means to move one of said Walls relative to the other wall;

(c) an elongated inlet port in each of said walls at said throat portion and communicating with said throat portion; and

(d) means whereby a lower pressure liquid at said throat portion may be thoroughly mixed with a higher pressure gas from said inlet ports, said latter means comprising flute means formed on each of said walls from immediately adjacent said throat portion toward said housing inlet, the fiute means on one wall being complemental and laterally offset from the flute means on the other wall so as to define between said walls a flow passage having a substantially uniform dimension in the direction which is transverse to the direction of liquid flow and parallel to the direction of gas flow through said inlet ports.

References Cited UNITED STATES PATENTS 1,526,041 2/ 1925 Bancel. 1,803,054 4/ 1931 Broido 94 1,832,652 11/1931 Pebbles. 2,751,974 6/ 1956 Stadler. 3 ,143 ,401 8 1964 Lambrecht. 3,219,325 11/1965 Brown.

HARRY B. THORNTON, Primary Examiner.

TIM R. MILES, Assistant Examiner. 

